[2023][ruby][16.x] golfing

2023/ruby/day_16.rb

@@ -11,38 +11,28 @@ count_energized = ->(start, dir) {
     coord, delta = current.shift
     seen << [coord, delta]
 
-    case [elem = input[coord], delta]
+    next_delta = case [input[coord], delta]
                  in [nil, _]
-      # the beam has escaped the contraption
+                   [] # the beam has escaped the contraption
                  in [?., _] | [?|, [_,0]] | [?-, [0,_]] # keep going
-      current << [coord.zip(delta).map { _1 + _2 }, delta]
+                   [delta]
                  in [?|, [0,_]] # split up and down
-      current << [coord.zip([-1,0]).map { _1 + _2 }, [-1,0]]
+                   [[-1,0], [1,0]]
-      current << [coord.zip([1,0]).map { _1 + _2 }, [1,0]]
                  in [?-, [_,0]] # split left and right
-      current << [coord.zip([0,-1]).map { _1 + _2 }, [0,-1]]
+                   [[0,-1], [0,1]]
-      current << [coord.zip([0,1]).map { _1 + _2 }, [0,1]]
+                 in [?/, _]
-    in [?/, [0,1]] # going right, goes up
+                   [delta.map { -_1 }.reverse]
-      current << [coord.zip([-1,0]).map { _1 + _2 }, [-1,0]]
+                 in [?\\, _]
-    in [?/, [0,-1]] # going left, goes down
+                   [delta.reverse]
-      current << [coord.zip([1,0]).map { _1 + _2 }, [1,0]]
-    in [?/, [1,0]] # going down, goes left
-      current << [coord.zip([0,-1]).map { _1 + _2 }, [0,-1]]
-    in [?/, [-1,0]] # going up, goes right
-      current << [coord.zip([0,1]).map { _1 + _2 }, [0,1]]
-    in [?\\, [0,1]] # going right, goes down
-      current << [coord.zip([1,0]).map { _1 + _2 }, [1,0]]
-    in [?\\, [0,-1]] # going left, goes up
-      current << [coord.zip([-1,0]).map { _1 + _2 }, [-1,0]]
-    in [?\\, [1,0]] # going down, goes right
-      current << [coord.zip([0,1]).map { _1 + _2 }, [0,1]]
-    in [?\\, [-1,0]] # going up, goes left
-      current << [coord.zip([0,-1]).map { _1 + _2 }, [0,-1]]
                  else
-      fail "unexpected element: #{elem.inspect}"
+                   fail
                  end
 
-    current = current.reject { seen.include?(_1) }
+    current.concat(
+      next_delta
+        .map {|d| [coord.zip(d).map { _1 + _2 }, d] }
+        .reject { seen.include?(_1) }
+    )
   end
 
   seen.map(&:first).select { input.has_key?(_1) }.uniq.size